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United States Patent |
5,558,095
|
Hynson
,   et al.
|
September 24, 1996
|
Method and device for increasing hand vascular resistance during blood
pressure measurement
Abstract
The vascular resistance to blood flow through the hand is increased in an
essentially uniform manner by the application of pressure to the hand. The
pressure is applied by means of an inflatable bladder mounted on an arm
board or within a non-expandable sleeve, mitten or glove, which bladder
covers at least the palm of the hand. Controlled inflation of the bladder
conveys pressure to the hand tissue to a degree necessary to compress
vascular structures and obstruct or restrict blood flow. By occluding
blood flow through the hand, more accurate invasive blood pressure
readings can be taken in clinical situations where decreased hand vascular
resistance occurs.
Inventors:
|
Hynson; James M. (1674 32nd Ave., San Francisco, CA 94122);
Katz; Jeffrey A. (1440 Madera Way, Millbrae, CA 94030)
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Appl. No.:
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520140 |
Filed:
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August 25, 1995 |
Current U.S. Class: |
600/561; 600/481 |
Intern'l Class: |
A61B 005/00 |
Field of Search: |
128/607,668,672,748
|
References Cited
Other References
Pauca, "Effect of Pethidine Premedication and Halothene Anesthesia on Upper
Limb blood flow," British Journal of Anesthesia, vol. 68, 1992, pp.
621-662.
Pauca, "Upper Limb Blood Flow During Hetamethonium Induced Hypotension"
British Journal of Anesthesia, vol. 60, 1988, pp. 151-156.
Hynson et al, "Thermoregulatory and Anesthetic-Induced Alterations in the
Differences Among Femoral, Radial, and Oscillometric Blood Pressures"
Anesthesiology, vol. 81, No. 6, Dec. 1984, pp. 1411-1421.
Pauca et al, "Reliability of the Radial Arterial Pressure During
Anesthesia: Is Wrist Compression a Possible Diagnostic Test?" Chest, Jan.
1994, vol. 105/1, pp. 69-75.
|
Primary Examiner: Sykes; Angela D.
Assistant Examiner: Nasser, Jr.; Robert L.
Attorney, Agent or Firm: Jones; William W.
Parent Case Text
This is a division of copending U.S. Ser. No. 08/297,301, filed Aug. 29,
1994.
Claims
What is claimed is:
1. A method for obtaining accurate blood pressure readings from a patient's
radial artery during periods of vasodilation of blood vessels in the hand,
said method comprising the steps of:
a) applying uniform pressure to the patient's hand so as to uniformly
restrict blood flow in the patient's hand to a degree necessary to elevate
blood pressure in a distal portion of the patient's arm to a level which
is comparable to aortic blood pressure; and
b) invasively measuring the patient's blood pressure in the radial artery
in said distal portion of the patient's arm while continuing to restrict
blood flow in the patient's hand.
2. The method of claim 1 wherein the uniform pressure is applied by
confining at least the palm of the patient's hand in an inflatable device,
and inflating the device to compress the palm of the hand so as to
restrict blood flow in the patient's hand.
3. The method of claim 2 wherein the device is inflated to a pressure which
equals or exceeds the expected systolic blood pressure of the patient.
Description
TECHNICAL FIELD
This invention relates to a method and apparatus for occluding blood flow
through the arterio-venous shunts in the hand so as to enable accurate
invasive blood pressure measurements to be obtained from the patient's
forearm. More particularly, this invention relates to a method and
apparatus for uniformly occluding blood flow through the hand by applying
external pressure to the hand by means of a selectively inflatable bladder
which covers at least the palm of the hand.
BACKGROUND ART
The physiologic basis for a wide variation in hand blood flow is the effect
of the thermoregulatory shunts on hand vascular resistance. The
thermoregulatory shunts are present in the fingers and palms. During
thermoregulatory vasoconstriction, these shunts are tightly closed and
hand blood flow is primarily determined by nutritional needs. During
thermoregulatory vasodilation, the shunts are open and provide a low
resistance arterio-venous path. During such vasodilation periods, blood
pressure measured invasively at the radial artery may not accurately
reflect central aortic pressure because the large increase in blood flow
along the brachial and radial arteries leads to a significant pressure
gradient from proximal to distal locations in the circulatory system.
There are a number of clinical situations when a patient's blood pressure
will be monitored invasively by means of an arterial blood pressure line
inserted in the patient's forearm, specifically, in the radial artery.
These situations include during surgery; in intensive or critical care
units; in cardiac care units; and in surgical recovery units, for example.
There are a number of common clinical situations in which problems arise
in obtaining accurate arterial blood pressure measurement from the
invasive arterial blood pressure line in the patient's forearm due to
increased blood flow through the hand, particularly through arterio-venous
shunts. These include anesthesia-induced vasodilation, hemodilution, use
of potent vasodialtors, sepsis, and hyperthermia. Several of these
conditions are present at the termination of cardiopulmonary bypass
surgery. The inability to accurately monitor arterial blood pressure at a
distal location by invasive means due to the presence of a significant
pressure gradient in the aforesaid clinical situations is a problem which
has not been addressed in a practical manner to date.
It would be highly desirable to provide a practical and readily controlled
method and apparatus for lessening the proximal-to-distal pressure
gradient in a patient's circulatory system to a degree wherein distal
invasive pressure measurements could be obtained which accurately reflect
aortic pressure.
DISCLOSURE OF THE INVENTION
This invention relates to a method and apparatus for selectively and
uniformly occluding blood flow through distal arterio-venous shunts
located in one's hand to a degree that will enable accurate arterial blood
pressure measurements to be made invasively from the radial artery in the
forearm during periods of hand vasodilation. The method preferably
involves the application of a uniform external pressure to at least the
palm of the hand so as to squeeze the hand sufficiently to occlude blood
flow to a degree which essentially prevents blood from flowing through the
arterio-venous shunts in the hand. By preventing or severely restricting
blood flow through the shunts, the resistance to blood flow through the
remainder of the arm is increased so that the blood pressure in the arm,
and particularly in the radial artery will more closely match the aortic
blood pressure.
The aforesaid external pressure is preferably applied to the hand by means
of an inflatable bladder which is positioned over at least the palm of the
hand. The bladder will have one component which faces away from the hand
and which is relatively non-stretchable so that it will not expand away
from the band when the bladder is inflated. The bladder will have another
component which contacts the palm of the hand and which is elastic so that
it will expand against the palm of the hand when the bladder is inflated.
The back of the hand will be restrained either by a non-elastic component
or sleeve on the bladder, or by an arm board which is fastened to the
patient's arm and hand. The bladder can be inflated manually by means of a
manually operated inflation bulb, or automatically by means of an
automated pump. The automated pump can be included in an otherwise
conventional automated non-invasive blood pressure monitor which may be
concurrently used to derive blood pressure readings from the patient's
upper arm. At times when the blood pressure readings are desired from an
invasive line inserted into the patient's radial artery, the
hand-pressurizing bladder will be inflated to pressures which preferably
exceed the patient's systolic blood pressure. When the hand has been
sufficiently occluded, the radial artery blood pressure measurements will
be taken. When the measurement procedure is finished, the bladder can be
deflated until the next time one desires to obtain the radial artery blood
pressure readings.
It is therefore an object of this invention to provide a method and
apparatus for use in uniformly increasing vascular resistance to blood
flow in the hand in order to obtain more reliable invasive distal blood
pressure measurements in the arm.
It is a further object of this invention to provide a method and apparatus
of the character described which involves applying a relative uniform
pressure to the exterior of the hand during periods of time when blood
pressure measurements are taken.
It is another object of this invention to provide a method and apparatus of
the character described wherein an inflatable bladder is selectively and
uniformly inflated on the hand so as to compress the palm of the hand
sufficiently to obtain the desired degree of vascular resistance to blood
flow in the hand.
It is yet another object of this invention to provide a method and
apparatus of the character described wherein the bladder is mounted on an
arm board or forms a part of a structure which encircles the hand and can
be used to constrain the hand relative To the bladder so as to ensure the
application of uniform pressure to the hand by the bladder.
These and other objects and advantages of the invention will become more
readily apparent from the following detailed description of several
embodiments of the invention when taken in conjunction with the
accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of an embodiment of the device used to retard or
occlude blood flow in the hand; and
FIG. 2 is a sectional view through the device showing the edge seals for
the bladder and the manner of construction of the remaining components of
the device.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION
Referring now to the drawings there is shown in FIG. 1 an example of a
blood flow retarding or restricting device formed in accordance with this
invention. The device is denoted generally by the numeral 2 and includes
an inflatable portion 4 which overlies at least the palm of the hand H,
and a hand constricting portion 6 which covers the back of the hand H. In
the embodiment shown in FIG. 1, the constricting portion 6 is an arm board
to which the arm of the patient is strapped; however, the constricting
portion 6 could also take the form of a non-elastic web or the like which
covers the back of the hand H. One side of the inflatable portion 4 may be
fixed to the arm board 6 as at 8, and the other side of the inflatable
portion 4 may be releasibly secured to the arm board 6 by closures such as
hook and loop assemblies 10. This arrangement will easily allow the device
2 to be affixed to or removed from the hand H. This embodiment of the
device 2 is designed to cover only the palm of the hand H; However, the
palm, thumb and fingers could be covered by the device as indicated by the
phantom line 2'. When a finger-covering embodiment is utilized, the
inflatable portion 4 can be permanently connected to the constricting
portion 6 throughout the entire overlying margin of the two portions so as
to form, in effect, a mitten-like device having an inflatable side and an
opposite constricting side. The inflatable portion 4 is provided with an
inflation/deflation hose 12 which is connected to a manually or automated
inflating device (not shown) so that the portion 4 can be selectively
inflated and deflated as desired. The line used for invasively measuring
the patient's arterial blood pressure is indicated by the numeral 14 and
communicates with the patient's radial artery in the vicinity of the
patient's wrist.
Referring now to FIG. 2, details of the construction and assembly of the
various components of the device 2 are shown in detail. As seen in FIG. 2,
the hand H is embraced by the arm board 6 and the inflatable portion 4
which overlies the hand H. The inflatable portion 4 includes an outer
non-elastic part 16 and an inner elastic part 18, the latter of which
contacts the hand H. The parts 16 and 18 are joined at their margins 20 so
as to form a bladder having an internal inflatable chamber 22. Strips 24
and 26 of the hook and loop closure 10 are adhered to the inflatable
portion 4 and the arm board 6 respectively so that, when the strips 24 and
26 are pressed together, the inflatable portion 4 will be held in the
position shown in FIG. 2 overlying the hand H. When the chamber 22 is
pressurized, the elastic part 18 of the device will press the hand H
tightly against the arm board 6 so as to restrict or occlude blood flow
through the hand H.
The device 2 can be operated in the following manner. The patient's arm and
hand H will be secured to the arm board in a normal manner, and the blood
pressure line 14 will be properly implanted in place in the patient's
forearm. The portion 4 of the device 2 will be brought into overlying
position relative to the patient's hand, and the closure strips 24 and 26
will be pressed together. At such times as it is desired to obtain the
patient's blood pressure measurements via the line 14, the portion 4 will
be pressurized so as to inflate the chamber 22 and press the elastic part
18 of the device 2 against the hand H. The chamber 22 will preferably be
pressurized to a pressure which is greater than the estimated systolic
pressure of the patient, thereby essentially occluding blood flow through
the patient's hand. This will provide increased resistance to blood flow
in the arm so as to elevate the blood pressure in the distal portions of
the arm to a value which will be comparable to actual aortic blood
pressure. While the hand is thus compressed, the invasive blood pressure
readings will be obtained through the line 14. At such times when distal
invasive blood pressure is not being monitored by the line 14, the device
can be deflated to allow blood flow through the hand.
It will be readily appreciated that this invention will allow the taking of
more accurate distal invasive blood pressure readings which will be more
indicative of actual aortic blood pressure during periods when
uncontrollable vasodilation of the blood vessels and shunts in the hand
are experienced. The actual cardiovascular condition of the the patient is
thus more accurately observed from the distal blood pressure readings so
that aortic cardiovascular abnormalities will be more apparent and more
readily detected by the invasive distal blood pressure readings. The
device can be used in conjunction with non-invasive blood pressure
monitors as a periodic confirmation or check of the accuracty of the
non-invasive blood pressure readings_ As previously noted, the device may
be configured without an arm board and may rely on a constricting sleeve
which covers the back of the hand. The device could also take the form of
a glove or mitten with or without the arm board, which covers the entire
hand of the patient.
Since many changes and variations of the disclosed embodiments of the
invention may be made without departing from the inventive concept, it is
not intended to limit the invention otherwise than as required by the
appended claims.
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